Last-Minute Changes Blur U.S. Digital Radio Spec

Welcome Guest. | Log In| Register | Membership Benefits

August 15, 2003 (1:10 PM EDT)

Last-Minute Changes Blur U.S. Digital Radio Spec

PARIS - Days before the launch of its heavily promoted digital radio system, iBiquity Digital Corp.-sole intellectual-property owner of the U.S. terrestrial digital broadcast scheme called HD Radio-earlier this week announced a fundamental change in the audio codec that is the heart of its system.

The last-minute switch was designed to quell growing doubts about HD Radio's fitness for broadcasts, and while some observers believe the HDC codec does the trick, skeptics said the system is still not ready for the airwaves.

The National Radio Standard Committee (NRSC) questioned the audio quality of iBiquity's original low-bit-rate PAC codec in May and then suspended its standards-setting process, with committee members bluntly saying they did not consider the audio quality of the proprietary 36-kbit/second codec fit for prime time.

But it's unclear whether the substitute can "clear the last technical hurdle," as iBiquity president and CEO Robert Struble hopes, before the Columbia, Md., company launches its digital radio technology on the consumer market.

Since HD Radio gained interim Federal Communications Commission authorization last October, 180 stations have signed up for broadcast licenses, with 50 stations already on the air. Kenwood, the first HD Radio receiver maker, was scheduled to launch its units in July but now says it won't deliver radios until early next year. For stations already on the air, the codec change can be implemented at the transmission side through "a CD software upgrade," said Struble.

The latest proprietary codec, he said, is based on "the core underlying audio-coding technology" the company inherited from Bell Labs when USA Digital Radio and Lucent Digital Radio merged as iBiquity in 2000. The HDC, which integrates Coding Technologies' Spectral Band Replication (SBR) to enable high sound quality at low bit rates, will be used in both digital AM and digital FM broadcasting.

Milford Smith, chairman of the NRSC's digital audio broadcasting subcommittee, said he was impressed by a recent HDC demo and endorses the codec choice. The National Association of Broadcasters (NAB), which co-sponsors NRSC standards setting along with the Consumer Electronics Association, includes among its members influential broadcasters such as ABC, Clear Channel and Viacom. All three of them are investors in iBiquity.

Despite Smith's enthusiasm for HDC, a coterie of radio and electrical engineers, radio station owners and others don't believe the eleventh-hour change in codecs solves what they see as HD Radio's system architecture problem. Their concerns center mainly on digital AM broadcasts, where critics point to questionable audio performance, sparse coverage and interference with adjacent analog channels.

Also, as of now, the nighttime usage of digital AM broadcasting remains unapproved by the FCC, due to the severe interference caused during the wee hours when stations from other cities are receivable.

Some groups advocate allocation of new spectrum for using Europe's Eureka 147-based digital audio broadcasting system in the United States. Others, according to petitions filed with the FCC, are suggesting alternative technologies. Kahn Communications, for example, says it has developed a digital AM broadcast system that promises 15-kHz audio fidelity, with full stereo, that's compatible with existing radios. Meanwhile, low-power FM supporters are fretting over how HD Radio might damage their own fledgling services.

The most fundamental question is how iBiquity's proprietary HD Radio system became the FCC's fair-haired boy in the first place, despite flaws in audio quality serious enough to force a late codec change. One answer is that HD Radio gained favor with regulators because it does not require them to allocate new broadcast spectrum as airwaves become more congested.

Initial NRSC tests showed that a station transmitting an HD Radio signal encountered very little interference. However, the same report mentioned that AM stations on first adjacent channels may encounter noticeable interference under certain listening conditions.

But HD Radio has never been tested against alternative systems. "Both the FCC and NAB appear to have rushed to judgment on a technology that was never compared to anything else," said Donald Schellhardt, a lawyer and a spokesman for the Amherst Alliance, a protest group that includes broadcasters, audio Webcasters and radio engineers.

Skip Pizzi, a columnist for the trade publication Radio World Online, wrote last year that from its beginnings, the system then known as IBOC, for in-band on-channel, "has been a closed development, created for and by commercial U.S. radio broadcasters."

Pizzi, also a manager responsible for media standards and regulation at Microsoft Corp., charged that "IBOC has been fundamentally a blocking policy, primarily intended to retain the status quo for incumbent broadcasters."

Because iBiquity's initial HD Radio reference platform is based on Texas Instruments Inc.'s TMS320DRI200 DSP, the codec upgrade can be as simple as replacing an external flash device that contains the audio algorithm, said John Gardner, worldwide marketing manager for digital radio at TI.

But iBiquity and TI still need to debug and integrate the new HDC onto TI's DSP. "We expect it to finish over the next 30 to 45 days," said iBiquity's Struble. TI's Gardner termed the codec change "a slight delay in the HD Radio rollout," and said TI played no part in suggesting a new codec.

Despite iBiquity's assurances about HDC, no data on audio performance improvement is publicly available. In an interview with EE Times, Struble simply said, "Digital FM, using the HDC, can now provide virtual CD quality, while digital AM can achieve the same level as analog FM."

Charles Hutton, a Seattle-based electrical engineer with expertise in modulation and audio coding, said Coding Technologies' SBR will "provide a clear improvement" over the earlier PAC technology. But "since the main codec is no longer PAC or AAC, there is no data or samples available to help us," he added. (AAC, part of the MPEG audio standard, was used during NRSC evaluation of the HD Radio system.) "That further clouds the water, and makes real-world tests the only way to be sure," Hutton said.

IBiquity said it has done "exhaustive tests" on HDC, although mostly subjective ones. Little field testing has taken place, but Struble said that is "less relevant" because the codec was changed only to improve sound quality and does not involve matters like signal propagation or interference.

Christopher Maxwell, vice president of the Virginia Center for the Public Press, begged to differ. Maxwell, who won an FCC license to operate a low-power FM station in Richmond, Va., believes iBiquity's HD Radio is designed to "wipe out competition."

The process of how the FCC authorized interim operation of stations even before developing formal rules has aroused suspicion in some quarters. NRSC's Smith said the FCC's decision rested on the standards body's initial favorable evaluations. However, during these evaluations, the audio codec used for both systems was AAC. Only afterward did iBiquity state plans to migrate the system to PAC.

The NRSC required follow-up testing to ensure that the change did not degrade performance, Smith said. "A formal evaluation of the FM PAC implementation showed performance comparable to the originally tested system with AAC," he said. But on the AM side, iBiquity withdrew the system data for PAC right after its initial submission. "Thus, the NRSC has not evaluated the AM system with the PAC codec," said Smith.

IBiquity's long list of big corporate sponsors sets off alarms among critics like Schellhardt, of the Amherst Alliance. He has charged conflict of interest among those who are investing in the technology while simultaneously evaluating it and praising it to the FCC.

"Even though they may have found the technology they've chosen is a turkey, they are saying that they could still impose the turkey on the public" Schellhardt said. The Amherst Alliance has petitioned the FCC to abandon IBOC and test alternative systems, such as Eureka or Digital Radio Mondiale.

Article appears courtesy of EE Times.